The chemical ingredients of a urethane foam system are a polyfunctional isocyanate and a polyhydric compound, along with catalysts necessary to control the rate and type of reaction, blowing agents necessary to control the rate at which gas is released, and surfactants necessary to stabilize the reaction. The reaction product when the polyfunctional isocyanate and the polyhydric compound are brought together is a polyurethane.
Polyurethane foams are produced using volatile liquids, usually chlorofluorocarbons, which act as blowing agents, producing gas on heating the foaming mixture. Besides acting as a blowing agent, the chlorofluorocarbons significantly reduce the overall polyhydric resin viscosity, thus allowing for easier processing. The problem with chlorofluorocarbons, however, is that they deplete the ozone layer of the upper atmosphere. Recently, the Environmental Protection Agency and local Air Quality Management Districts have stepped up their efforts to regulate the amount of chlorofluorocarbons (CFC's). Any reduction of chlorofluorocarbons from urethane foam products will help achieve acceptable environmental conditions, and help prepare the industry for the probability of more stringent air pollution regulations in the future.
The eventual elimination of chlorofluorocarbons, however, presents a serious concern to urethane foam producers since non-chlorofluorocarbon blowing agents such as water and methylene chloride, do not have the dual effect of functioning as blowing agents and reducing the viscosity of polyhydric resins. In contrast, the present inventors have unexpectedly discovered that replacing some portion of the hydroxyl groups on the polyhydric compounds with acetoacetate groups significantly reduces the viscosity of the polyhydric resins without deleteriously effecting the reactivity of the polyhydric resins or the performance properties of urethane foam products made therefrom.
U.S. Pat. No. 5,051,529 discloses the use of the acetoacetate moiety in coatings to impart functionality capable of undergoing a variety of cross-linking reactions while simultaneously lowering the viscosity of the resulting formulation. However, the effect of acetoacetylation on polyurethane foams has never been determined.